The flow characteristics of nozzles, particularly nozzles used with compressible fluids, cannot be calculated precisely. To calculate the flow characteristics of a given nozzle, it is necessary to later measure the nozzle in order to determine the flow rate as a function of pressure. However, the flow characteristics need to be determined very precisely. Thus, while it is simple to measure the pressure accurately, the volumetric flow of the fluid is difficult to determine.
It is known to determine the volumetric flow of a nozzle by using fluid sources, in which the flow of a fluid arriving from a critically operated nozzle is conveyed to the nozzle to be tested by means of laminar flow elements. Although this measuring arrangement is comparatively accurate, it is not suitable as a measurement standard for calibration purposes.